ScienceShot

ScienceShot: The Secret History of the Domesticated Apple

Nearly every child has bitten into a crabapple (left) at some point and spit it back out—yuck! But a new study in PLoS Genetics shows that modern supermarket apples (right) are more closely related to crabapples than to other, better-tasting ancient species. Apples originated in Kazakhstan, where they show incredible variety in taste and size, then spread along the Silk Road trading route thousands of years ago. The Romans brought sweet apples from western Asia into Europe (Europeans previously used the fruit for cider), but the domesticated apple's history was murky after that. The new study looked at rapidly evolving DNA regions known as microsatellites in 839 apple samples representing five species ranging from Spain to China. Testing these microsatellites allowed scientists to tease out the impact of recent crossings with wild apples. The researchers confirmed that modern apples were first domesticated from wild Asian apples, but they found that subsequent crosses with European crabapples—possibly selected for disease resistance, hardiness, or other traits—contributed the most DNA to modern domesticated apples. The scientists also found no evidence of genetic bottlenecks—a severe narrowing of genetic diversity—in domesticated apples, a pattern that contrasts with the earliest domesticated crops like barley, millet, and wheat.